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DOI: 10.5593/SGEM2016/HB63/S08.021

A MODEL OF INACTIVATION OF LACTOBACILLUS PLANTARUM IN A LIQUID WITH AND WITHOUT VEGETABLE SOURCE OF PREBIOTIC

M.G.Gordienko, B.A. Karetkin, D.V. Baurin, N.G. Loiko, V.I. Panfilov
Friday 11 November 2016

References: 16th International Multidisciplinary Scientific GeoConference SGEM 2016, SGEM Vienna GREEN Extended Scientific Sessions, www.sgemviennagreen.org, SGEM2016 Conference Proceedings, ISBN 978-619-7105-79-7 / ISSN 1314-2704, 2 - 5 November, 2016, Book 6 Vol. 3, 161-168pp, DOI: 10.5593/SGEM2016/HB63/S08.021

ABSTRACT
Saving of viable lactobacilli cells count for a long period is one of the main quality indicators of food and feed probiotic products. Microbial death is known to be much higher in hydrated than freeze-dried culture state. In our study Lactobacillus plantarum inactivation in the liquid mediums when stored during 8 weeks was investigated. Fermentation was carried in a nutrient medium containing 25 or 50% v/v of milk whey after casein acid precipitation, and also 2 g/L of yeasts extracts. Pulp (10% w/v) (particle size about 1 mm) obtained after inulin extraction from Jerusalem artichoke was added as lowering inactivation factor to the nutrient medium. Thereby the problem of rational usage of plant processing by-products has been solved. Lactobacillus fermentation was carried out at 28 °C, without stirring during 48 hours that corresponded to a prolonged stationary growth phase. Lactobacillus count had no significant difference (about 1×109 CFU/ml) at any medium composition. Thus, dramatic difference took place after storage of suspension obtained at +5 °C during 8 weeks. In particular, high concentration of nutrients in media caused the increase of inactivation rate, while the presence of solid particles had a positive effect on Lactobacillus stability.
Lactobacillus inactivation kinetic curves obtained experimentally were different depending on whether Jerusalem’s artichoke pulp was added to the medium or not. In case of heterogeneous submerged fermentation (Jerusalem’s artichoke pulp) the microorganism inactivation function during the storage period did not have inflection point and had a shape of descending curve. To describe this curve the Weibull model was applied. In the second case, the curve was supposed to vary on the second week that was due to culture dissociation into ‘weak’ and ‘strong’ populations. It is to be noted that dissociation of the population (different shapes of the colonies) was observed when counting of lactobacilli grown on medium containing 25% of whey only, however the percentage of the minor variant did not exceed 7%.
To consider the dissociation phenomenon the sum of two Lactobacillus populations was considered, each was described by Weibull model. Model parameters were determined as the result of experimental data mathematical processing, tenfold decrease in population being shown in the form of regression depending on concentrations of milk whey and Jerusalem artichoke pulp. The standard deviation of values calculated from the experimentally obtained ones at the chosen linear approximation was 0.3.

Keywords: Lactobacillus plantarum, inactivation, Jerusalem artichoke, optimisation, Weibull distributions, plant processing by-products

PAPER DOI: 10.5593/SGEM2016/HB63/S08.021, A MODEL OF INACTIVATION OF LACTOBACILLUS PLANTARUM IN A LIQUID WITH AND WITHOUT VEGETABLE SOURCE OF PREBIOTIC

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